Field of the Invention
The present invention relates to an image lens, and particularly to an inner focus macrolens suitable as an image lens of a camera, and an image pickup device using such a lens.
Description of the Related Art
Lenses used in photographic cameras and still video cameras include wide-angle lenses and standard lenses. As such wide-angle lenses or standard lenses, Gauss lenses have been conventionally proposed. In a Gauss lens, refractive powers are substantially symmetrically disposed with respect to an aperture stop.
Wide-angle lenses and standard lenses generally have focusing functions. Examples of the focus type include an inner focus type. Gauss lenses can also employ the inner focus type. In this case, some of the lenses disposed closer to an image than an aperture stop is move.
In the inner focus type, a lens to be moved is a relatively light-weight lens. In the case of moving a plurality of lenses, a relatively small number of lenses move. Thus, the inner focus type is advantageous because of its increased focusing speed and reduced cost.